Pressure relief vent



p 1961 R. P. SHEPHERD ETAL 3,001,537

PRESSURE RELIEF VENT Filed April 27, 1960 a m- I? INVENTORS.

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3,001,537 PRESSURE RELIEF VENT Raymond P. Shepherd, Loveland, and Robert W. Guertin,

Cincinnati, Ohio, assignors to OPW Corporation, Cincinnati, Ohio, a corporation of Ohio Filed Apr. 27, 1960, Ser. No. 25,025 6 Claims. (Cl. 137-73) This invention relates to pressure relief vents and more particularly to a pressure relief vent incorporating a blowoff disc operative under conditions of excessive heat and/or pressure to permit the escaping gases to be blown upwardly into the atmosphere rather than downwardly about the vent as is customary under normal operating conditions.

A principal object of the instant invention. is the provision of an emergency pressure relief vent particularly adapted for use on above ground storage tanks for volatile liquids, such as gasoline. The invention find utility in conjunction with the bulk storage of any hazardous liquid subject to vaporization. While it is normally desirable to seal the tank against the free exchange of air with the outside atmosphere, it is nevertheless necessary to prevent the build-up of excessive pressure in the tank which might rupture its walls. In order to avoid such pressure build-up, the instant invention provides a normally closed yet displaceable pressure cap arranged to open under a predetermined pressure. The pressure cap is of umbrella shape so that, when displaced upwardly, the gaseous mixture will be expelled downwardly about the periphery of the cap. In normal operation the cap acts as a cover preventing rain and the like from entering the open vent. However, in the event of a fire or other condition which would require that the escaping gases be directed away from the tank rather than downwardly around the pressure cap, the vent is provided with a blow-out disc formed from brass or other soft metal and secured to the cap by means of a fusible metal seal. Thus in the event of a fire and the ignition of the escaping gas, the blow-out disc will be displaced and the gases will be blown upwardly away from the tank.

The foregoing, together with other objects of the invention which will be set forth hereinafter or Which will be apparent to the skilled worker in the art upon reading these specifications, are accomplished by that construction and arrangement of parts of which an exemplary embodiment will now be described. Reference is first made to the accompanying drawings wherein:

FIG. 1 is a vertical sectional view of a pressure vent in accordance with the invention, the pressure cap being shown in normally closed position.

FIG. 2 is a vertical sectional view similar to FIG. 1 illustrating the pressure cap in displaced or normally open position.

FIG. 3 is also a vertical sectional view illustrating the positioning of the parts in the event the blow-out disc is ruptured.

Referring first to FIG. 1 of the drawings, the vent comprises a body having a base 1 terminating at its lower end in a collar 2 internally threaded, as at 3, to receive a standard pipe. The base 1 terminates upwardlynn an annular flange 4 having a shoulder 5 against which the rim of a fire screen 6 is adapted to seat. The fire screen is of generally cup-shape, as indicated at 7, and extends downwardly within the base 1.

The vent body is provided with a top or dome 8 terminating downwardly in an annular flange 9 adapted to make sealing contact with the flange 4 of the base. The base and dome are detachably secured together by a plurality of bolt assemblies, one of which is indicated generally at 10, the assemblies each comprising an eye bolt 11 pivotally connected by means of a pin 12a to a lug 12 forming an integral part of the dome 8, the eye bolt being secured to a lug 13 integrally formed with the;

base 1 by means of wing nut 14. It will be understood, of course, that the manner in which the parts are secured together does not constitute a limitation on the invention, although it is desirable that the base and dome parts he A spider 16 extends inwardly from the Walls of the dome and supports a centrally disposed vertically extending sleeve 17 which slidably receives the pilot rod 18, the upper end of which is in threaded engagement withthe hub 19 of a spider 20 forming a part of the pressure cap 21.

The pressure cap 21 is of umbrella or dome shape and has a centrally disposed opening 22 therein the free area of which is also substantially equal to the area of r the vent pipe. The pressure cap is provided with a seat ring 23 which, when the cap is in the position illustrated in FIG. 1, seats against the uppermost end of the dome 8 about the periphery of the opening 15.

The opening 22 in the pressure cap is closed by a blow-01f disc 24, preferably formed from a soft metal such as brass, the disc being joined to the cap by a fusible metal seal 25.

In the operation of the device, the pressure cap will normally seat against the dome, thereby closing the opening 15 in the top of the dome 8. The pressure at which the cap 21 may be displaced will be determined by its weight; and this may be readily adjusted by altering the mass of its walls so that it will be displaceable at one pound pressure or at whatever other pressure is desired. When the pressure within the body of the vent overcomes the weight of the pressure cap, the cap will be displaced upwardly, being guided by the pilot rod 18 which also limits the extent of its upward movement, the pilot rod being provided at its lower end with a cotter pin 26 or other stop means which will effectively engage the lowermost end of the sleeve 17.

The normally open position of the pressure cap is illustrated in FIG. 2 wherein it will be seen that the pressure generating gaseous mixture will be vented upwardly through the vent opening 15 and then downwardly around the skirt of the pressure cap. When the excess pressure has been relieved, the weight of the pressure cap will return it to its lowermost position, thereby reclosing the vent opening 15.

In the event of a fire or other emergency condition, the pressure cap will first move to the position of FIG. 2, but if sufiicient heat is present to melt the fusible metal seal 25 or otherwise displace the blow-01f disc 24, the gases will then flow upwardly through the now uncovered opening 22 and the body of the pressure cap '21 will, under its own weight, move downwardly so as to reseat itself in the manner illustrated in FIG. 3, the entire force of the expelled gases thus being directed upwardly away from the storage tank.

As should now be apparent, the instance device provides a simple and inexpensive pressure relief vent having a pressure-responsive cap, which also incorporates a blow-off disc which becomes operative under extreme conditions. The construction of the device is such that the blow-01f disc may be readily replaced at nominal cost.

Having thus described the invention in an exemplary Patented Sept. 26, 1961 a 3 embodiment, what is desired to be secured and protected by Letters Patent is:

1. In a pressure relief vent, a body terminating at its lower end in a fitting of a size to receive a vent pipe, said body terminating atits upper end in a 'vent opening, a pressure cap' overlying said' vent opening, means mounting said'pressure' cap for limited vertical movement from a first position in which said cap is seated against the upper end of said body so as to close said vent opening, to a second position in which said cap is displaced upwardly from said -vent opening soas to permit gases to flow outwardly between said vent opening and said cap, a centrally disposed openingin said cap invertical' alignment with said vent opening, and 1a blow-oil disc normally closing the opening in said cap, said blow-01f disc being sealed to said cap bymeans of a low melting point fusible metal,

2. The device claimed in claim I wherein said vent opening and the opening in said cap-have a substantially equalflow area, which flow areais substantially equal to the flow area of said lower end of the body.

3. The device claimed in claim 1 wherein said pressure cap is of dome shape and is of a size to form a protective umbrella for said vent opening when in said second position.

4. A pressure relief vent comprising a body terminatingatits lower end in a fitting of a size to receive a vent pipe, said body terminating at its upper end in a vent opening, a spider in said body slidably mounting,

a centrally disposed vertically movable pilot rod, a pressure cap secured to the upper end of said pilot rod, said pressure cap being movable with said pilot rod from a first position in which said cap is seated against the upper end of said body so as to close said vent opening, to a second position in which said cap isr displaced upwardly from said vent opening so as to define a vent passageway. therebetween, saidpressure cap being of dome; shape so as to provide an umbrella like cover for said: vent opening, a centrally disposed opening in said pressure cap in vertical alignment with said vent opening, the opening in said cap being normally closed by a blow-off disc secured to said cap by means of a fusiblemetal seal.

5. The pressure relief vent claimed in claim 4 wherein said vent body is composed of upper and lower parts,

wherein means are provided to detachably secure the upper and lower parts together, wherein said upper part mounts said spider and pilot rod, and wherein said lower part supports a cup-shaped fire screen.

6. The pressure relief vent claimed in claim 5 wherein the open flow area of said vent opening and the opening in said cap are substantially equal to each other and to the cross sectional area of said lower end of the body.

References Cited in the file of this patent UNITED STATES PATENTS 

